The present invention relates to a method and a device for controlling the transmission operation of an automatic transmission, and more specifically, to an automatic transmission operation control designed to perform transmission operation by alternating the connection between friction engagement elements, in which the control for releasing a friction engagement element and for connecting another friction engagement element is carried out simultaneously.
Heretofore, an automatic transmission is known that is designed to control the connection and release of friction engagement elements through hydraulic pressure, and to perform the transmission operation by alternating the connection between friction engagement elements, in which the connection control and the release control of two friction engagement elements are carried out simultaneously (refer for example to Japanese Unexamined Patent Publication Nos. 6-341526 and 9-133205).
Even further, a transmission operation control technique appropriate for performing upshift transmission operation during a power-on status is disclosed in Japanese Patent Application Laid-Open Publication No. 6-011028.
Even during the same upshift transmission operation or downshift transmission operation, it is preferred that the transmission operation control characteristics or the engine torque control request during transmission operation and the like be varied, depending on whether the transmission operation is a power-on state transmission operation or a power-off state transmission operation, as disclosed in the above-mentioned Publication No. 6-011028. According to the prior art, the power-on state and the power-off state are determined according to the step-in quantity of the accelerator pedal (throttle opening).
The power-on state refers to the state where the driving wheel is rotated by the engine through a transmission mechanism, and the power-off state refers to the state where the driving wheel is not rotated by the engine.
The engine torque may be estimated based on the step-in quantity of the accelerator pedal. However, the estimated torque may differ from the actual engine torque. Therefore, according to the conventional method, it is difficult to determine the engine torque with high accuracy. Even further, the basis of judgement for the step-in quantity has to be changed according to various driving conditions, and therefore, there has been a need for a process related to selecting the basis of judgement. However, if the wrong basis of judgement is selected, the judgement resulting therefrom is also erroneous.
The present invention is aimed at solving the above-mentioned problems. The object of the invention is to provide a method and a device for accurately and easily determining whether the transmission operation is a power-on state transmission operation or a power-off state transmission operation, and properly switching the characteristics and the like of the transmission operation control accordingly.
Moreover, the object of the invention is to provide a method and a device for carrying out a suitable transmission operation process based on the determined result of whether the transmission operation is a power-on state transmission operation or a power-off state transmission operation.
In order to achieve the above objects, the present invention determines whether the transmission operation is a power-on state transmission operation or a power-off state transmission operation based on the direction to which the input shaft rotation speed changes when starting the release control of the release-side friction engagement element. Based on the determined result, different transmission operation processes are selected for different determination results.
According to such configuration, the invention determines whether the transmission operation is a power-on state (driven state) transmission operation in which the driving wheel is rotated by the engine, or a power-off state (non-driven state) transmission operation in which the driving wheel is not rotated by the engine. The determination is performed based on the direction to which the rotation speed of the input shaft (turbine rotation speed) changes when the release-side friction engagement element is released.
As the power-on/power-off state is determined based on the direction to which the input shaft rotation speed changes, there is no need to determine the level of the engine torque, and no need to adapt a judgement basis in order to determine the power-on/off status accurately and easily. Therefore, the present invention enables to accurately select the best transmission operation process.
Moreover, in order to achieve the above objects, the present invention is designed to compute the gear ratio based on the input/output shaft rotation speed of the transmission mechanism, and based on the direction of change of the gear ratio when the release control of the release-side friction engagement element is started, determination is made on whether the transmission operation is a power-on state transmission operation or a power-off state transmission operation. Based on the determination, the best transmission operation process is selected.
According to such feature of the invention, by determining the direction of change of the gear ratio, the direction of change of the input shaft rotation speed is determined indirectly, which leads to determining whether the transmission operation is a power-on transmission operation or a power-off transmission operation. When the power-on/power-off of the transmission operation is judged based on the direction of change of the gear ratio, there is no need to determine the level of the engine torque, and no need to adapt a judgement basis in order to determine the power-on/off status accurately and easily. Therefore, the present invention enables to accurately select the best transmission operation process.
Moreover, according to the invention, the term xe2x80x9cgear ratioxe2x80x9d refers to gear ratio=input shaft rotation speed/output shaft rotation speed.
Even further, based on the determined power-on/power-off status, the present invention selects either the release-side friction engagement element or the connection-side friction engagement element as the main object of control when changing the gear ratio to a post-transmission operation gear ratio.
The other objects and phases of the present invention will become apparent from the following description on the preferred embodiments of the invention with reference to the accompanied drawings.